jmri: version-aware install/upgrade via marker file

Replace binary-exists check with .jmri_installed_version marker pattern.
- Reads marker on each run; skips install if version matches
- On version mismatch: stops JMRI, wipes /opt/JMRI, downloads new archive
- Separates build hash into jmri_build_hash var (templated into download URL)
- Config is preserved — lives in git-managed .jmri symlink
To upgrade: bump jmri_version + jmri_build_hash, re-run playbook.

ansible/roles/jmri/defaults/main.yml

@@ -1,8 +1,12 @@
 ---
 # JMRI version to install
+# Update both jmri_version AND jmri_build_hash together when upgrading.
+# Find the build hash in the release asset filename on:
+# https://github.com/JMRI/JMRI/releases
 jmri_version: "5.10"
+jmri_build_hash: "ca461bd266"
 jmri_install_dir: /opt/JMRI
-jmri_download_url: "https://github.com/JMRI/JMRI/releases/download/v{{ jmri_version }}/JMRI.{{ jmri_version }}+Rca461bd266.tgz"
+jmri_download_url: "https://github.com/JMRI/JMRI/releases/download/v{{ jmri_version }}/JMRI.{{ jmri_version }}+R{{ jmri_build_hash }}.tgz"
 
 # Service user
 jmri_user: jmri